Flocking involves the embedding of a short length of filament fiber, called flock, in an adhesive layer covering a fabric substrate. A wide range of natural and synthetic fibers can be used as flock including rayon, cotton, nylon, and polyester.
Flock is traditionally applied by three main methods; mechanical flocking, direct current electrostatic flocking and alternating current electrostatic flocking. In mechanical flocking, the flock fibers sift down onto a coated substrate that is simultaneously subject to a vigorous beating on its underside. The beating causes the substrate to vibrate which in turn causes the flock fibers to orient vertically and embed in the adhesive.
AC and DC electrostatic flocking use high voltages in the range of 30,000 volts to 120,000 volts. In both electrostatic methods, flock fibers are delivered from a hopper into the electrostatic field. The flock fibers receive a positive charge from the electrostatic field (alternating with a negative charge in AC electrostatic flocking) and are driven into the neutrally or ground potential charged adhesive coating.
Attempts have been made by the AC electrostatic flocking art to improve production speeds, pile density, and surface uniformity, as well as to reduce the amount of unattached or excess flock accumulating during fabrication. To this end, modifications have been made to the shape and size of the electrostatic grids, the electrostatic finish on the fiber and the composition of the adhesive. No attention, however, has been directed towards adjusting the frequency of the alternating electrostatic field. AC flocking is conventionally operated at 60 Hz. U.S. Pat. No. 2,376,922 discloses that 25 Hz and other frequencies will provide satisfactory results; no prior art teaching, however, teaches or suggests selectively adjusting the frequency of the alternating electrostatic field to accomplish the aforementioned objectives.